Our lawn has recently been invaded by "spiderwebs". I can't explain it. I've never actually seen any spiders in the lawn. From 6 to 8 feet away, the "webs" (which are in the grass) look like flat, round, ripped up plastic bags. The webs are 4 to 6 inches in diameter, and there are between 15 and 20 webs. This happens at least three times a year, and never at the same time. It's happened during December, March, July, October, January, whatever.
I put "webs" in quotes because the other possibility is that this is some sort of fungus. The one that immediately comes to mind is Sclerotinia minor - however, these webs are much more sparse and thinly-packed than any sclerotinia I've ever seen. That, and I've only seen sclerotinia as a lettuce pathogen - something like this on grass is rather bizarre. I don't think it's snow mold either, but I could be wrong.
If you've ever seen anything resembling either possibility, tips for killing the offenders would be much obliged.